Electrostatic discharge (ESD) protection is becoming ever more important as integrated circuits become smaller and smaller. There are several ways in which to provide ESD protection, each having their own advantages and disadvantages. For example, ESD can be provided by a silicon controlled rectifier (SCR). A SCR is a solid state switching device that turns current on and off.
A semiconductor diode's behavior in a circuit is given by its current-voltage characteristic. The shape of the curve is determined by the transport of charge carriers through the so-called depletion layer or depletion region that exists at the p-n junction between differing semiconductors. The width of the depletion region cannot grow without limit. If an external voltage is placed across the diode with the same polarity as the built-in potential, the depletion zone continues to act as an insulator, preventing any significant electric current flow. This is the reverse bias phenomenon. However, if the polarity of the external voltage opposes the built-in potential, recombination can once again proceed, resulting in substantial electric current through the p-n junction (i.e., substantial numbers of electrons and holes recombine at the junction). At very large reverse bias, beyond the peak inverse voltage, a process called reverse breakdown occurs. This causes a large increase in current (i.e., a large number of electrons and holes are created at, and move away from the pn junction) that usually damages the device permanently.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove.